Rotary crop residue spreaders for agricultural combines are well known in the art. Commonly, such spreaders are of the horizontal type, that is, they include one or more horizontal disks supported for rotation about an axis oriented vertically or at a small acute angle to vertical, and a plurality of radially extending blades attached to an upper surface of the disk for receiving straw from the threshing system of the combine and/or chaff from the cleaning system and directing a flow of the residue sidewardly and/or rearwardly from the spreader. Reference in this regard, the spreaders shown in U.S. Pat. Nos. 6,406,368; 6,343,986; and 6,209,808. Reference also U.S. Pat. No. 4,591,102 which discloses a horizontal chaff spreader including blades rotatable in a horizontal plane above a base plate for receiving crop residue blown and/or dropped from above and accelerating and discharging the residue through sidewardly directed  chutes. An advantage of the known horizontal crop residue spreaders is that the crop residue, be it straw and/or chaff, essentially falls from above into the spreader such that induction and mixing of the crop residue for acceleration and discharge from the spreader is not problematic. However, a disadvantage of the known horizontal type crop residue spreaders such as those disclosed above, include that they have a relatively large forward to rearward horizontal extent, and must be located beneath an outlet or other pathway of crop residue from the spreader, for instance, a rear opening to a cleaning system of the combine, so as to make access to the cleaning system and other components in the rear of the combine inconvenient and more difficult than is desirable.
To overcome the above referenced disadvantages, it is desired to utilize a vertical spreader, that is, one including accelerating apparatus or elements that rotate in a vertical plane, or a plane oriented at only a small acute angle to vertical, about a rotational axis oriented horizontally or at a small acute angle to horizontal generally less than about 45 degrees, and located in a rear opening of a combine. It is also desired for the spreader to be to movable away from the opening to allow access to the cleaning system and other components in the rear of the combine. However, by using the vertical orientation, the spreader must have the capability for simultaneously receiving or inducting both the heavier, bulkier crop residue discharged from the threshing mechanism of the combine, which heavier residue typically includes straw, husks, cobs, stems, and the like and is typically propelled rearwardly by a rapidly rotating and powerful beater or straw walker and is deflected downwardly toward the rear opening of the combine, and the lighter, fluffier, and  less bulky chaff which includes pod fragments and the like which are separated by the cleaning system from the grain or other crop and blown much more gently rearwardly toward the rear opening.
More particularly, typically, the straw and other heavier, bulkier crop residue is blown or propelled rearwardly from the threshing region with considerable force, and then is deflected downwardly toward the rear opening. In contrast, the chaff and other crop residue from the cleaning system is propelled much less forcefully, using air flow from a fan, as it is not desired for the grain or other crop, which is relatively lightweight, to be blown out of the rear opening and lost. It is typical to desire for the crop residue to be spread relatively evenly over the swath of the combine as it moves along a field, it being possible for a swath to have an extent of 40 feet or more for some large farming operations. Therefore, for a vertical spreader including two counter-rotating crop accelerating elements, it would be expected for each element to be capable of propelling crop residue a distance equal to about one-half of the combine swath, or up to as much as 20 feet or so, in the instance of the larger combines. To achieve such a propulsion requirement, it is necessary for the rotary accelerating apparatus to be rotated at a relatively high rotational speed. It is also desirable for blades or other impellers of the rotary accelerating apparatus to be sufficiently large for handling anticipated volumes of crop residue, particularly the bulkier material from the thresher. However, vertical crop residue spreaders including rapidly rotating rotary accelerating apparatus having such relatively large blades have been found to generate an undesirable back pressure condition forwardly of the blades in the region for receiving and  inducting the chaff from the cleaning system, which results in a build-up of crop residue in that region and even blow back of crop residue into the cleaning system area. Also, a less than desirable degree or level of rearward flow of air through the rear opening of the combine may be achieved, which can cause an undesirable dust buildup in the more forward chassis region of the combine.
Still another variable to be factored when using a vertical spreader which is not as problematic for a horizontal spreader is the size and rearward extent of the rear wheels of the combine. That is, some combines have driven rear wheels and/or may be larger machines so as to require larger rear wheels that extend rearwardly to beside the rear opening of the combine. As a result, for the sideward discharge of the spreader to pass the larger rear wheels it may be required to tilt the spreader rearwardly to an orientation at an angle to vertical. This can result in at least the lower portion of the spreader being located farther rearwardly of or in the rear opening, such that desired air and chaff flow characteristics into the spreader are more difficult to achieve.
Thus, what is sought is apparatus that overcomes the problems, shortcomings and disadvantages set forth above.